So Ethernet has been a relatively inexpensive, reasonably fast and very popular LAN technology for,
gosh, several decades.
It was commercially introduced in 1980 and first standardized in 1983 as I triple E 802.3.
And has since been refined to support higher bit rates and longer link distances.
Ethernet has since become the most popular and probably the most widely deployed network technology
in the world.
Many of the issues involved with Ethernet are common to many network technologies and understanding
how Ethernet addresses these issues can build a foundation that will improve your understanding of networking
in general.
So let's keep the design principles of Ethernet simple.
The basic idea of its design is that multiple computers have access to it and can send data at any time.
If two computers send data at the same time, a collision will occur.
So and when this happens, the data set is is not going to be usable.
In general, both computers will stop sending and wait a random amount of time before they'll try again.
Now a special protocol was developed to deal with such problems.
It's called Carrier sense Multiple access with collision detection.
Or it might be easier to say Csma CD.
Today, Ethernet cables look like, well, thick telephone cables.
Modern cables connect to hubs or switches, and each cable runs from a computer's network interface
card, the Nic to such a box.
Now, here are the most widely known Ethernet cables ten base two and ten base five cables are what
I would call retro coaxial cables.
You don't see them much today.
Each computer has a T plugged into it and cables plug into each side of that t.
Ten base t 100 base t 1000 base t are all unshielded twisted pair or UTP cables, which look a lot like
thick phone cables, and they go from each computer to a hub or a switch.
Initial numbers indicate the supported speed so that ten will stand for ten megabits per second, and
1000 stands for 1000 megabits, also known as gigabit or one gigabit.
In base F cables are the same as ten base T, but they are fiber cables and they'll transmit light pulses
instead of electrical signals over copper.
A data packet on an Ethernet link is called an Ethernet packet, which transports an Ethernet frame
as its payload.
An Ethernet frame is preceded by a preamble and start frame Delimiter or SFD, which are both part of
the Ethernet packet at the physical layer.
Right.
There are four types of Ethernet frames.
And the most common one is the Ethernet to frame, also known as Dic's frame.
We're talking about the Ethernet two frame at the moment.
Each Ethernet frame starts with.
An Ethernet header which contains destination and source Mac addresses as its first two fields.
The middle section of the frame is payload data, including any headers for other protocols.
For example, internet protocol carried in the frame.
The frame ends with a frame check sequence or FCS, which is a 32 bit cyclic redundancy check used to
detect any in-transit corruption of data.